What Are the Effects of Ultraviolet Light on Bacteria Mortality

Abstract The objective: The purpose of this experiment was to observe the effects of short term ultraviolet light exposure on bacteria. Methods/Materials Escherichia coli (E. coli) and Serratia marcescens cultures were prepared by a technician at the University of California San Diego biology laboratory. I plated and labeled the samples and exposed the bacteria to ultraviolet light (at 254 nm) for two, five, and 30 minutes. Trypticase soy agar was used as the culture medium. The samples were plated. Half of each disk was exposed to ultraviolet light and half of each plate was shielded, so that each plate would serve as its own control. The experiment was repeated using only the Serratia marcescens strain and shorter lengths of exposure times (15 seconds, 30 seconds, and one minute) to the 254 nm ultraviolet light in an attempt to establish at what exposure time mortality begins. Results After incubation, bacteria on the side not exposed to ultraviolet light (the shielded side) were observed to have grown into distinct, visible colonies. None of the bacteria exposed to ultraviolet light for two, five, or 30 minutes at 254 nm survived. When the experiment was repeated, bacteria mortality was approximately 40-75% for Serratia marcescens exposed to ultraviolet light (at 254 nm) for 15 seconds and about 75-90% bacteria mortality for the 30 second exposure. One minute of exposure time to ultraviolet light resulted in 95-99% bacteria mortality. Therefore, complete mortality for Serratia marcescens is probably a little longer than one minute, but less than two minutes. Conclusions/Discussion Ultraviolet light exposure for short time periods, such as two or five minutes, was not expected to completely destroy the bacteria. Similarly, it was not expected that bacteria exposed to ultraviolet light (254 nm) for one minute would result in almost complete mortality. Surprisingly, very low exposure times, such as 15 and 30 seconds resulted in at least 40% bacteria mortality and bacteria exposed to 254 nm for one minute resulted in at least 95% mortality. This project is to observe the effects of short term ultraviolet light exposure at 254 nm on Serratia marcescens and E. coli bacteria.

Study of the Health Benefits of Spicy Cooking

Abstract The objective: People in equador regions use spices in food preparation for thousands of generations. By using these spices, are they keeping themselves healthy by keeping their food "clean?" My objective is to find out if spices have the ability to kill food-spoilage microorganisms. And if they do, which spices are most effective and by how much? This is what I plan to find out after I have conducted my experiment. Methods/Materials My experimental setup was designed to test volatile emission from the spices. After obtaining agar dishes, E. coli, and sterile swabs from CSUF, I carefully streaked E. coli on all of my dishes. Then I turned them upside down and I applied 1/4 tsp. of spice on the lid. I used all of the following spices: cinnamon, garlic, mustard, black pepper, coriander, lemon juice, and chilli powder. Then I left my dish at 27 degrees Celsius for 4 days. I had three replicates. Results The results of my experiment show that not all of the seven spices used were effective. Complete Inhibition- coriander 100%. Partial Inhibition- mustard 83%, cinnamon 67%, lemon juice 67%, black pepper 17%, and garlic 17%. None- chilli powder 0%. Conclusions/Discussion According to my results, spices do have antibacterial properties, but not all of them. This is potentially beneficial in tropical countries that have ineffective food storage methods. This project is to see whether spices have antibacterial properties.

Beleaguered Beef

Abstract The objective: The objective was to determine whether or not there is a difference between naturally grown ground beef and standard ground beef in terms of antibiotic additives. I hypothesized that the standard ground beef would show usage of antibiotic additives while the naturally grown ground beef would not. Methods/Materials I swabbed five agar dishes with the juice from standard and natural ground beef. The standard ground beef types were Porter's Premium and Raley's. The natural ground beef types were Coleman Natural, Whole Foods lean, and Whole Foods leanest. Additionally, I used one agar dish as a control, in which I did not swab it with the variable. I then incubated all six agar plates over a period of five days. From the growth of bacteria on each agar plate, I concluded whether or not antibiotics were used.. Results In terms of percentage of bacterial growth covering the agar plates, the naturally grown ground beefs averaged 31 percent of their entire agar plates. Next, the standard ground beefs averaged 30 percent. Finally, the control averaged 20 percent. At times the some of the naturally grown ground beefs cultured fewer amounts of bacteria than some of the standard ground beefs. I attribute this to the fact that there is usually more effective sanitation in natural beef factories than in standard ones. Conclusions/Discussion My hypothesis was proven correct in that the naturally grown ground beefs cultured more bacteria because they had little or no antibiotic additives. Reversely, the standard ground beefs cultured less bacteria because of the presence of antibiotic additives. As much research states, antibiotic additives in meat are dangerous and should be prohibited. When humans consume this meat they risk health problems and possibly even death. My investigation proves that it is much healthier to eat naturally grown ground beef than standard ground beef. Therefore this finding could be very benefical to the public. This project is to find whether or not there is a difference between naturally grown ground beef and standard ground beef in terms of antibiotic additives.

Which Acne Medications Are Most Effective

Abstract The objective: The objective is to determine which acne medications are the most effective in inhibiting the growth of Propionibacterium acnes, over-the-counter or prescription. Methods/Materials The active ingredients of two prescription antibiotics, three over the counter acne medications and two plant extracts were tested in vitro in duplicate two separate times against P. acnes. The bacterium was incubated under anaerobic conditions in the presence of disks containing the study medications and a control disk. The diameter of each inhibition zone was measured to the nearest millimeter and recorded. Results Tetracycline was the most effective, with an average inhibition zone of 46.25 mm, followed by Clindamycin with a 45.5 mm inhibition zone. Surprisingly, Oregano oil had the third largest inhibition zone of 31.25 mm. Benzoyl peroxide 10%, Benzoyl peroxide 2.5%, the equal mix of Tea Tree oil and Oregano oil followed with inhibition zones of 24.75 mm, 23 mm, and 19.67 mm zones, respectfully. Lastly, with inhibition zones of 0 mm were the control, Salicylic acid, and Tea Tree oil. Conclusions/Discussion The prescription acne medications are the most effective in vitro against Propionibacterium acnes. This project compares the in vitro effectiveness of prescription verses over- the -counter acne medication aginst Propionibacterium acnes.

Study of Bacteria Growth in Varying Acidic Environments

Abstract The objective: The objective of my project was to discover the effect that liquids of different acidities would have on the growth of bacteria found on raw meat. It was predicted that the stronger the acid, the more the growth of the bacteria would be inhibited. Methods/Materials Petri dishes were prepared with an agar-broth mixture. Six different solutions, water, vinegar, 0.5 normal HCl, 1 normal HCl, pure lemon juice, and lemon juice diluted with an equal part of water, were prepared, and their pH measured. Pieces of chicken, each approximately 1 cubic centimeter, were placed in each liquid for two minutes. The chicken pieces were then removed, and each one rubbed over the surface of a Petri dish. Other pieces of chicken not dipped in any solution, were also rubbed against the surfaces of five Petri dishes, for comparison. The Petri dishes were then sealed. After four days, the lids were removed from the Petri dishes, and the percent of surface area covered in visible bacteria colonies was measured. Results There were no visible bacteria colonies on the surfaces of the Petri dishes rubbed with chicken dipped in 1 normal HCl, while the 0.5 normal HCl showed the next least amount of bacteria growth. The Petri dishes rubbed with chicken dipped in pure lemon juice had a larger amounts of bacteria than those rubbed with chicken dipped in diluted lemon juice and vinegar. The Petri dishes rubbed with chicken dipped in water grew the most bacteria out of the chicken dipped in any solution, while the Petri dishes rubbed with chicken not dipped in anything had the most bacteria. Conclusions/Discussion My conclusion is that stronger acids tend to inhibit bacterias growth, unless there is another affecting factor, such as the sugar in the lemon juice, which seems to have affected the speed at which the bacteria grew. This project is a study of the effect that different acidic solutions have on the growth of bacteria found on raw chicken.

What Is the Best Way to Clean Your Toothbrush

Abstract The objective: My objective was to determine the best way to clean your toothbrush. My investigative question was whether or not washing your toothbrush in water would get rid of all the germs. My hypothesis was that the toothbrush cleaner would work better at cleaning a toothbrush and eliminating germs than plain water. Methods/Materials I had my family take turns spitting in a cup until there was about 1-½ inches of spit in the cup. I dipped 12 toothbrushes into the cup and let them sit in plastic bags for 2 days. I divided the toothbrushes into four groups: control group (doing nothing), water group (rinsing the toothbrush in hot tap water for 10 seconds), Aqua Blast group (soaking a toothbrush in Aqua Blast for 10 minutes) and dishwasher group (placing toothbrush in top rack of dishwasher using Cascade soap). I pressed each toothbrush into a petri dish with nutrient agar solution. I repeated the experiment 2 more times. My Dad supervised me during the experiment and I wore protective gloves. Results I took pictures of the petri dishes at 30 hours and 75 hours. Using a scale of 1 to 10, I rated the amount of bacteria where 1 had no bacteria and 10 had a lot of bacteria. I completed tables and charts and computed the average amount of bacteria for each group. By assigning numerical values, I was able to determine which method worked best at cleaning a toothbrush and eliminating germs. Conclusions/Discussion The Aqua Blast did work better at cleaning a toothbrush and eliminating germs than plain water; however, I was surprised that the dishwasher method worked best. I was also surprised that rinsing your toothbrush off with water was not much better than doing nothing at all to your toothbrush after brushing. Most people simply rinse their toothbrushes off with water; I think they would change their habits if they saw the results of my experiment. I concluded that the dishwasher method was best, was more cost effective and may be safer for you and the environment. This project was to determine the best way to clean your toothbrush.

How Much Bacteria Is on Your Retainer

Abstract The objective: The goal of our science project was to see if time and brushing effected the amount of bacteria growth on retainers. Methods/Materials First we gathered ten test subjects that were willing to be a part of our experiment. Then, we gave them directions as to what to do. Following that, we took samples of the bacteria colonies from each of their retainers. Thus, with the help of the Sansum laboratory and Dr. Jane we were able to incubate the bacteria colonies. Results After spending many hours in the laboratory counting bacteria samples, we came to realize, the longer the retainer is in ones mouth without being brushed, the more bacteria is present. We found this by incubating the bacteria and then counting each colony that appeared on the petri dishes. We noticed that the students who wore their retainers for 4 hours had less bacteria than the people who wore their retainers for 16 hours. Furthermore, the people that did not brush their teeth had more bacteria then the people who did brush their teeth. Conclusions/Discussion We came to the conclusion that time and brushing do effect the amount of bacteria growth on retainers. The longer the retainer is in ones mouth without being brushed the more bacteria will be produced. This is because bacteria feeds of plaque and one develops plaque when they do not brush their teeth. This project was about the effects that time and brushing had on the amount of bacteria present on ones retainer.